Wow! that is a thorough information onDOS. Can you submit a presentation entirely on locus distributed operating system and amoeba distributed operatiing system. i have these topics in my semester. we have been taught on what is distributed operating system, but a disytrubuted operating system ppt is much more understandable than classroom lectures.

Network Operating System It provides an environment where users are aware of the multiplicity of machines.
Users can access remote resources by
logging into the remote machine OR
transferring data from the remote machine to their own machine
Users should know where the required files and directories are and mount them.
Each machine could act like a server and a client at the same time.
E.g NFS from Sun Microsystems

6 :

Distributed Operating System Runs on a cluster of machines with no shared memory
Users get the feel of a single processor - virtual uniprocessor
Transparency is the driving force.
Requires
A single global IPC mechanism
A global protection mechanism
Identical process management and system calls at all nodes
Common file system at all nodes

7 :

DOS: Transparency Location Transparency
Users are not aware of the positioning of the resources in the system.
Migration Transparency
Resources can move without changing names
Replication Transparency
Users should not be aware of the presence of multiple copies of a resource
Failure Transparency
Masking the partial failures in the system
Performance Transparency
Reconfiguring the resources to improve the performance of the system

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Transparency Contd... Concurrency Transparency
Resource sharing is automatic
Parallelism transparency
Activities can happen in parallel without the knowledge of the user. He sees only speedup.
Scaling Transparency
Allowing the system to expand in scale without distrupting the activities of the users

Group Communication One to many communication
Multicast/Broadcast
Open group/Closed group
Flexible reliability
The 0-reliable
The 1-reliable
The m-out-of-n reliable
All reliable
Atomic Multicast
Many to one communication
Many to many Communication
Absolute Ordering (Global clock)
Consistent ordering (Sequencer/ABCAST protocol)
Causal ordering

19 :

Design Issues Resource management
It is impossible to gather information about utilisation or availability of resources coherently.
Hence these have to be calculated approximately using heuristic methods.
Processor allocation
Load balancing
Hierarchical organisation of processors.
If a processor can’t handle a request, ask the parent for help.
Issues: Crashing of a higher level processor will result in isolation of processors attached to it.

20 :

Design Issues
Process scheduling
Communication dependency has to be considered.
Fault tolerance
The design should consider distribution of control and data.
Services provided
Typical services include name, directory, file, time, etc.